Method for producing a particulate carrier material provided with elementary silver and elementary ruthenium

ABSTRACT

The invention relates to a method for producing a particulate carrier material provided with silver and ruthenium, comprising the following steps: a) providing a water-insoluble particulate carrier material and aqueously dissolved silver and ruthenium precursors, b) bringing the particulate carrier material into contact with the aqueous solution of the precursors to form an intermediate, c) bringing the intermediate into contact with an aqueous hydrazine solution having a pH of &gt;7 to 14 to form a mass comprising silver and ruthenium, d) optionally washing the obtained mass, and e) removing water and other possible volatile components from the mass.

The invention relates to an efficient method for producing a particulate carrier material provided with elemental silver and elemental ruthenium.

WO 2007/139735 A2 discloses a method for producing nano/microparticles with a core-shell structure. The particles comprise a non-metal core with a transition metal/precious metal shell. The transition metals/precious metals are selected from copper, nickel, silver, palladium, platinum, ruthenium, gold, osmium and rhodium. The particles can be produced by providing a transition metal salt/precious metal salt solution, dispersing nano/microparticles in the salt solution, evaporating the solvent to obtain a slurry comprising coated nano/microparticles, adding a reducing agent to the slurry, and drying the slurry.

WO 2007/142579 A1 discloses a polymer matrix comprising an electron donor and metal particles comprising at least one metal selected from the group consisting of palladium, gold, ruthenium, rhodium, osmium, iridium and platinum. The electron donor can be at least one non-precious metal, for example silver. The production method disclosed is the sequential deposition of silver and at least one further metal selected from the group consisting of palladium, gold, ruthenium, rhodium, osmium, iridium and platinum. The deposition is carried out in each case from a suspension of the metal particles in question by bringing into contact with the polymer matrix.

WO 2009/044146 A1 discloses a material comprising metal nanoparticles supported on a porous polysaccharide derivative, said nanoparticles having a diameter of 1 to 30 nm. The metal of the nanoparticles can be a precious metal. The material can be produced by adding the porous polysaccharide to a solvent, adding a salt of the metal in question, stirring the mixture at elevated temperature and separating off the supported nanoparticles from the mixture.

The object of the invention was to provide an efficient process that can be scaled up to a production level for producing a particulate carrier material provided with elemental silver and elemental ruthenium. Carrier materials equipped in this way can be used as additives for antimicrobial finishing of a very wide variety of materials and substances, for example in or on metal surfaces, coating agents, plasters, molding compounds, plastics, synthetic resin products, silicone products, foams, textiles, cosmetics, hygiene articles and much more besides.

The object can be achieved by a method for producing a particulate carrier material provided with elemental silver and elemental ruthenium, comprising the following successive steps:

-   -   a) providing a water-insoluble particulate carrier material         and (i) an aqueous solution A comprising dissolved silver         precursors (for the sake of conciseness, also referred to         hereinafter in the description and the claims simply as “aqueous         solution A”) and an aqueous solution B comprising dissolved         ruthenium precursors (for the sake of conciseness, also referred         to hereinafter in the description and the claims simply as         “aqueous solution B”) or (ii) an aqueous solution comprising         both dissolved silver precursors and dissolved ruthenium         precursors (for the sake of conciseness, also referred to         hereinafter in the description and the claims simply as “aqueous         solution C”),     -   b) bringing the water-insoluble particulate carrier material         into contact (i) with aqueous solution A and aqueous solution B         or preferably (ii) with aqueous solution C to form an         intermediate, preferably an intermediate in the form of a         free-flowing impregnated particulate material,     -   c) bringing the intermediate into contact with an aqueous         solution comprising a pH in the range of >7 to 14, preferably         of >11 to 14, and comprising hydrazine, to form a mass         comprising elemental silver and elemental ruthenium,     -   d) optionally washing the mass obtained after completion of step         c), and     -   e) removing water and other possible volatile components from         the mass obtained after completion of step c) or d).

From another perspective, the method according to the invention can also be understood as a method for providing a particulate carrier material with elemental silver and elemental ruthenium, comprising the successive steps a) to e).

Steps a) to e) are successive steps and may be directly successive steps without intermediate steps.

In step a) of the method according to the invention, a water-insoluble particulate carrier material and (i) said aqueous solutions A and B or (ii) said aqueous solution C are provided. It is preferable to provide aqueous solution C. It is superfluous per se to the person skilled in the art to mention that the particulate carrier material is present in the solid state of matter.

The carrier material particles can have a wide variety of particle shapes. For example, they can be irregularly shaped or they can have a defined shape, for example spherical, oval, platelet-shaped or rod-shaped. The carrier material particles may be porous and/or comprise cavities, or neither of these. They can have a smooth or rough or structured outer surface. The carrier material particles can have an average particle size (d50) for example in the range from 20 to 100 μm. The term “average particle size” means the average particle diameter (d50) determinable by means of laser diffraction. Laser diffraction measurements can be performed with a corresponding particle size measuring device, for example a Mastersizer 3000 from Malvern Instruments. The absolute particle sizes generally are no less than 1 μm, and they generally do not exceed 1000 μm.

The water-insoluble particulate carrier material has a more or less large water absorption capacity between the particles and optionally also within the particles, for example within pores and/or in depressions of the particle surface. The water-insoluble particulate carrier material can be swellable with water or even capable of forming a hydrogel with water.

For the person skilled in the art, it is already clear from the term “water-insoluble carrier material” that the water-insoluble actual carrier material is impervious not only to water, but also to the chemicals with which it comes into contact in the method according to the invention; otherwise, it would in principle not be able to successfully perform the function of a carrier material or that of a water-insoluble carrier material. It is selected such that it is not attacked, dissolved or impaired in its property as a carrier material by water or by said chemicals or chemical combination. The water-insoluble actual carrier material per se is preferably a non-water-repellent material. It is preferably hydrophilic, but as stated in any case water-insoluble. The actual carrier material can be a material selected from inorganic or organic substances or materials, in each case in particle form, for example as a powder. In order to prevent any misunderstandings, the carrier material is a silver-free and ruthenium-free substance or a silver-free and ruthenium-free material. Examples include glass; nitrides such as aluminum nitride, titanium nitride, silicon nitride; high-melting oxides such as aluminum oxide, titanium dioxide, silicon dioxide, for example as silica or quartz; silicates, for example sodium aluminum silicate, zirconium silicate, zeolites; plastics, for example (meth)acrylic homopolymers and copolymers and polyamides; modified or unmodified polymers of natural origin, for example polysaccharides and polysaccharide derivatives, in particular cellulose and cellulose derivatives; carbon substrates, in particular porous carbon substrates; and wood.

Cellulose powder is a preferred particulate carrier material, in particular in the form of linear cellulose fibers with a fiber length in the range of, for example, 10 to 1000 μm.

The aqueous solution A provided in step a) (i) comprises dissolved silver precursors and the aqueous solution B also provided in step a) (i) comprises dissolved ruthenium precursors.

For the person skilled in the art, it is already clear from the term “aqueous solution A” that this is a solution and not for example a disperse system; in other words, aqueous solution A typically does not comprise any undissolved substances, i.e. also no sediments or precipitates. Aqueous solution A is characterized in that, in addition to water as solvent, it also comprises one or more silver(I) compounds dissolved therein. The silver(I) compounds and optionally any desired or undesired substances present in aqueous solution A are typically selected such that aqueous solution A as is, and preferably also in combination or contact with aqueous solution B, comprises no sediments or precipitates, and that such sediments or precipitates do not form.

For the person skilled in the art, it is already clear from the term “aqueous solution B” that this is a solution and not for example a disperse system; in other words, aqueous solution B typically does not comprise any undissolved substances, i.e. also no sediments or precipitates. Aqueous solution B is characterized in that, in addition to water as solvent, it also comprises one or more ruthenium compounds dissolved therein. The ruthenium compounds and optionally any desired or undesired substances present in aqueous solution A are typically selected such that aqueous solution B as is, and preferably also in combination or contact with aqueous solution A, comprises no sediments or precipitates, and that such sediments or precipitates do not form.

The aqueous solution C preferably provided in step a) (ii) comprises both dissolved silver precursors and dissolved ruthenium precursors. For the person skilled in the art, it is already clear from the term “aqueous solution C” that this is a solution and not for example a disperse system; in other words, aqueous solution C does not comprise any undissolved substances, i.e. also no sediments or precipitates. Aqueous solution C is characterized in that, in addition to water as solvent, it also comprises one or more silver(I) compounds dissolved therein and one or more ruthenium compounds dissolved therein. The silver(I) compounds and the ruthenium compounds and optionally any desired or undesired substances present in aqueous solution C are selected such that aqueous solution C comprises no sediments or precipitates, and that such sediments or precipitates do not form.

Silver precursors and ruthenium precursors are one or more silver(I) compounds and one or more ruthenium compounds. The one or more ruthenium compounds are selected from the group consisting of ruthenium(II) compounds, ruthenium(III) compounds and ruthenium(IV) compounds; in particular, they are ruthenium(III) compounds.

The silver(I) compounds and ruthenium compounds serving as silver precursors and ruthenium precursors are those from which elemental silver or elemental ruthenium can be produced by means of the reducing agent hydrazine. Examples include silver acetate, silver nitrate, silver sulfate, ruthenium acetate and ruthenium nitrosylnitrate. Ruthenium chloride is suitable as a constituent of the aqueous solution B, but is not preferred therein; it is not suitable as a constituent of aqueous solution C. A particularly preferred combination of said precursor is that of silver nitrate with ruthenium nitrosylnitrate, both together in aqueous solution C and in the combination of aqueous solution A with aqueous solution B.

The aqueous solutions A and B provided separately are used in combination in step b); within this combination, for example, in a weight ratio in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium.

The silver weight fraction in aqueous solution A is, for example, in the range from 0.5 to 20 wt % (% by weight).

The ruthenium weight fraction in aqueous solution B is, for example, in the range from 0.5 to wt %.

The silver:ruthenium weight ratio in aqueous solution C is, for example, in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium and in this case generally significantly in favor of the silver. This silver:ruthenium weight ratio is also still found in the process product obtained after completion of step e), i.e. the particulate carrier material provided with elemental silver and elemental ruthenium.

The silver plus ruthenium weight fraction in aqueous solution C is, for example, in the range from 0.5 to 20 wt %.

In step b) of the method according to the invention, the water-insoluble particulate carrier material is brought into contact with (i) aqueous solutions A and B or preferably (ii) aqueous solution C to form an intermediate, preferably an intermediate in the form of a free-flowing impregnated particulate material.

The intermediate is a mixture of the water-insoluble particulate carrier material and (i) aqueous solutions A and B or preferably (ii) aqueous solution C. Depending on the mixing ratio, the intermediate can have different forms, for example that of a pulp-like, paste-like or dough-like mass, or that of a slurry. In a preferred embodiment, however, the intermediate is a free-flowing impregnated particulate material and step b) is designed accordingly.

The term “free-flowing impregnated particulate material” used herein describes a material in the form of grains or flakes impregnated (i) with aqueous solutions A and B or preferably (ii) with aqueous solution C, each of which grains or flakes comprises or can consist of one or more particles of the original particulate carrier material. The free-flowing impregnated particulate material is not liquid: it is not a liquid dispersion or suspension; rather, it is a free-flowing material in the manner of free-flowing powder.

The free-flowability of the free-flowing impregnated particulate material can be investigated by means of rotary powder analysis. To this end, a cylindrical measuring drum can be filled with a defined volume of the free-flowing impregnated particulate material. The measuring drum has a defined diameter and a defined depth. The measuring drum rotates about the horizontally-oriented cylinder axis at a defined constant speed. One of the two end faces of the cylinder, which together enclose the filled free-flowing impregnated particulate material filled in the cylindrical measuring drum, is transparent. Before the start of the measurement, the measuring drum is rotated for 60 seconds. For the actual measurement, images of the free-flowing impregnated particulate material are subsequently taken, during rotation, along the axis of rotation of the measuring drum using a camera with a high frame rate of, for example, 5 to 15 images per second. The camera parameters can be selected in such a way that the highest possible contrast at the material-air interface is achieved. During the rotation of the measuring drum, the free-flowing impregnated particulate material is entrained against the force of gravity up to a certain height before it flows back into the lower part of the drum. The flowing back takes place in a slip-like (discontinuous) manner, and is also referred to as avalanching. A measurement is ended when the slipping of a statistically relevant number of avalanches, for example 200 to 400 avalanches, has been registered. Subsequently, the camera images of the free-flowing impregnated particulate material are evaluated by means of digital image analysis. In rotary powder analysis, the “avalanche angle” and the duration between two avalanches (“avalanche time”) can be determined as parameters which are characteristic of the free-flowability. The avalanche angle is the angle of the material surface as the avalanche falls down, and thus represents a measure of how high the free-flowing impregnated particulate material will stack up before this stack collapses in the manner of an avalanche. The duration between two avalanches corresponds to the time elapsed between the occurrence of two avalanches. A suitable tool for performing said rotary powder analysis and for determining the avalanche angle and the duration between two avalanches is the Revolution Powder Analyzer from PS Prozesstechnik GmbH, Neuhausstrasse 36, CH-4057 Basel. The operating instructions and recommendations included with the instrument should be followed. Typically, the measurement is carried out at room temperature, or 20° C. The free-flowing impregnated particulate material formed in step b) of the method according to the invention can have an avalanche angle, determined using a 100 mL test amount of said free-flowing impregnated particulate material and using said device at 0.5 rpm and using a cylinder with an internal depth of 35 mm and an internal diameter of 100 mm, in the range of 40 to 80 degrees; the duration between two avalanches in this case can for example be in the range from 2 to 5 seconds and can represent another characterizing feature of the free-flowability of the free-flowing impregnated particulate material.

The particulate carrier material can be added to aqueous solution A and/or to aqueous solution B, or vice versa. The sequential, alternating or simultaneous addition of aqueous solutions A and B to the initially charged particulate carrier material is preferred. In general, mixing is carried out during, and also after, the addition, for example by stirring.

In the preferred case of working with aqueous solution C, the particulate carrier material can be added to aqueous solution C or vice versa. Preference is given here to adding aqueous solution

C to the initially charged particulate carrier material. In general, mixing is carried out during, and also after, the addition, for example by stirring.

In the preferred embodiment of the formation of an intermediate in the form of a free-flowing impregnated particulate material, it is important to proceed in step b) such that, after completion of step b), no pulp-like, paste-like or dough-like mass and also no slurry are obtained, but rather the free-flowing impregnated particulate material is formed in the form of a product that is homogeneous when viewed macroscopically. The free-flowability of the free-flowing impregnated particulate material can, for example, depend on its grain size, the surface properties of its particles and the content of the latter on aqueous solution A plus aqueous solution B or on aqueous solution C.

When step b) is carried out, it is expedient to provide sufficient time to mix the particulate carrier material and (i) aqueous solution A and aqueous solution B or (ii) aqueous solution C. For example, it may be expedient to mix, in particular to stir, for a sufficient amount of time after the addition has ended. In the case of the preferred embodiment with the formation of the intermediate in the form of a free-flowing impregnated particulate material, the mixing is expedient until said homogeneous, in particular visually homogeneous state of the mixed material is achieved when viewed macroscopically. The actual addition can take place, for example, as metered addition with mixing. Generally applicable time information for metering rates and mixing times cannot be specified here because of the dependence on the relevant batch size and the type of components to be mixed, in particular the type of particulate carrier material.

When step b) is carried out according to the preferred embodiment, the volume (i) of aqueous solution A and aqueous solution B or (ii) of aqueous solution C can be adaptively selected via the relevant concentration of the amount of particulate carrier material to be brought into contact therewith and its absorption behavior for the aqueous solution(s). Such a procedure can contribute to the fact that, in the subsequent step c), the elemental silver and the elemental ruthenium can be deposited as completely as possible in and/or adhering to the particulate carrier material. If an excessively large volume or volumes is (are) selected, the above-mentioned less preferred or even undesired pulps, doughs, pastes or slurries arise rather than the intermediate in the preferred form of the free-flowing impregnated particulate material. The person skilled in the art can easily determine the absorption behavior of a relevant particulate carrier material for a corresponding aqueous solution in orienting laboratory experiments and thus determine the upper limit in liters of aqueous solution per kilogram of particulate carrier material without any loss of free-flowability occurring. Generally applicable information on the absorption behavior of the particulate carrier material for (i) aqueous solutions A and B or (ii) aqueous solution C cannot be made here because of the dependence on the nature of the components to be mixed, in particular depending on the nature of the particulate carrier material.

Preferably, the successive steps b) and c) are directly successive steps without intermediate steps, in particular without a removal of water from the intermediate taking place in between, which intermediate is preferably present in the form of the free-flowing impregnated particulate material.

In step c) of the method according to the invention, the intermediate obtained after completion of step b) or the preferred free-flowing impregnated particulate material is brought into contact with an aqueous solution comprising a pH in the range of >7 to 14, preferably of >11 to 14, and comprising hydrazine (for the sake of conciseness, also referred to hereinafter in the description and the claims simply as “aqueous hydrazine solution”), to form a mass comprising elemental silver and elemental ruthenium.

The pH of the aqueous hydrazine solution is particularly preferably in the range from 12 to 14.

The basic pH of the aqueous hydrazine solution can be adjusted with a strong base, in particular with a corresponding amount of alkali metal hydroxide, especially sodium hydroxide or potassium hydroxide.

The hydrazine can be added as is, more precisely as hydrazine hydrate, in the preparation of the aqueous hydrazine solution, or as hydrazinium salt, for example as hydrazinium chloride or preferably as hydrazinium sulfate, from which hydrazine is released by means of the strong base.

The hydrazine concentration of the aqueous hydrazine solution is for example generally in the range from 0.1 to 5 wt %, typically in the range from 0.2 to 1 wt %.

In general, the aqueous hydrazine solution does not comprise any other ingredients besides water, hydrazine and a base. If the hydrazine originates from a hydrazinium salt, the corresponding salt formed from the base and hydrazinium salt is also included.

1 mol of the reducing agent hydrazine can deliver 4 mol of electrons having a reducing effect and accordingly releases 1 mol of N₂ upon reduction. Accordingly, for example, for the reduction of 1 mol of Ag⁺, 0.25 mol of hydrazine are required, and for the reduction of 1 mol of Ru³⁺, 0.75 mol of hydrazine are required.

The aqueous hydrazine solution is brought into contact with the intermediate or with the free-flowing impregnated particulate material in a stoichiometrically required amount, or more, but preferably no more than 110% of the stoichiometrically required amount, for complete reduction of the silver and ruthenium precursors contained in the intermediate or in the free-flowing impregnated particulate material.

In this case, the aqueous hydrazine solution can be added to the intermediate or to the free-flowing impregnated particulate material, or vice versa. Preference is given to adding the aqueous hydrazine solution to the initially charged intermediate or to the initially charged free-flowing impregnated particulate material. The addition can take place at a temperature for example in the range from 15 to 50° C. The reduction of the silver and ruthenium precursors to elemental silver and elemental ruthenium takes place directly upon contact with the hydrazine. The reduction of the silver and ruthenium precursors takes place at the same time. During and preferably even after the end of the addition, for example up to 1 hour after the end of the addition, mixing is usually carried out, for example by kneading and/or stirring. In general, the end of the reduction can be recognized by no more nitrogen being released.

The method can be carried out in such a way that the mass comprising elemental silver and elemental ruthenium formed in step c) is a suspension or a slurry. However, it is also possible to carry out the method in such a way that the mass comprising elemental silver and elemental ruthenium formed in step c) comprises only a small amount of free liquid or even does not contain any free liquid; for example, it is possible to this end to work with a volume of the aqueous hydrazine solution which is adapted using the concentration. “Not containing free liquid” means that the mass comprising elemental silver and elemental ruthenium, in the rest state, does not undergo phase separation in the sense of a separate aqueous phase forming as a supernatant above the mass comprising elemental silver and elemental ruthenium, even after 10 minutes.

In the optional but preferred step d) of the method according to the invention, the mass comprising elemental silver and elemental ruthenium obtained after completion of step c) can be washed, in particular by washing with water. In this case, water-soluble constituents can be removed, for example the base, any excess hydrazine and other water-soluble constituents.

In step e) of the method according to the invention, water and any other volatile constituents present are removed from the mass obtained after completion of step c) or from the washed mass obtained after completion of step d).

The removal of the water can take place in the sense of virtually complete removal of water or in the sense of removal of water until a desired residual moisture content is reached. To this end, the majority of the water can first be removed by customary methods such as squeezing out, press filtration, straining out, centrifuging or other processes which act similarly, before drying, optionally supported by reduced pressure, at temperatures for example in the range from 20 to 150° C.

As a direct product of the method according to the invention, i.e. after completion of step e), a particulate material or carrier material provided with elemental silver and elemental ruthenium is obtained. Depending on the nature of the originally used particulate carrier material, the silver and the ruthenium can be present on inner surfaces (within pores and/or cavities) and/or on the outer surface of the originally silver-free and ruthenium-free carrier material particles and, for example, form a continuous or discontinuous layer and/or small silver or ruthenium particles. The silver and ruthenium are not present in alloyed form in this case, but rather are randomly distributed. It is clear to the person skilled in the art that the silver and the ruthenium can comprise other silver species than elemental metal silver and other ruthenium species than elemental metal ruthenium at the surface thereof, for example corresponding oxides, halides and/or sulfides. Such species can be formed while the method according to the invention is carried out or subsequently, for example during storage, use or further processing of the process product. The silver plus ruthenium weight fraction of the process product can vary within wide limits, for example in the range from 0.1 to 50, preferably 1 to 40 wt %, and the process product can at the same time have a silver:ruthenium weight ratio for example in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium. The person skilled in the art will understand, after reading the disclosure herein, which variable parameters and which variation possibilities are thus available to them when carrying out the method according to the invention, in order to produce process products with a desired silver plus ruthenium weight fraction and with a desired silver:ruthenium weight ratio in a desired batch size, for example on the single-digit ton scale. Using the example of the preferred way of carrying out the method, with aqueous solution C, such variable parameters include in particular:

-   -   type and amount of the particulate carrier material used in step         b),     -   volume of aqueous solution C used in step b),     -   silver:ruthenium weight ratio in aqueous solution C,     -   silver plus ruthenium weight fraction in aqueous solution C, and     -   residual moisture of the process product obtained after         completion of step e).

The first step of the person skilled in the art is therefore initially the selection of the type of particulate carrier material and the determination of target values for the silver and ruthenium content in the end product. Thereafter, the person skilled in the art will determine the batch size and select a corresponding amount of particulate carrier material which is to be provided with elemental silver and elemental ruthenium according to the procedure according to the invention. As soon as these selections have been made, they can define the other variable parameters accordingly and carry out the method according to the invention with aqueous solution C. When carrying out the method with aqueous solutions A and B, analogous considerations apply.

For example, when cellulose powder is used as particulate carrier material, the method according to the invention can be used to produce cellulose powders provided with elemental silver and elemental ruthenium with a silver plus ruthenium weight fraction for example in the range from 0.1 to 50 wt %, preferably 1 to 40 wt %, in the case of a silver:ruthenium weight ratio for example in the range from 1 to 2000 parts by weight of silver:1 part by weight ruthenium efficiently and in batch sizes in the range of up to 5 tons, for example.

The invention also relates to the products produced by the method according to the invention and to the use thereof as additives for antimicrobial finishing of: metal surfaces; coating agents; plasters; molding compounds; plastics in the form of plastics films, plastics parts or plastics fibers; synthetic resin products; ion exchange resins; silicone products; cellulose-based products; foams; textiles; cosmetics; hygiene articles and many others. The cellulose-based products can be selected, for example, from the group consisting of paper products, cardboards, wood fiber products and cellulose acetate, and the plastics can be selected, for example, from the group consisting of ABS plastic, PVC (polyvinyl chloride), polylactic acid, PU (polyurethane), poly(meth)acrylate, PC (polycarbonate), polysiloxane, phenol formaldehyde resin, melamine formaldehyde resin, polyester, polyamide, polyether, polyolefin, polystyrene, hybrid polymers thereof, and mixtures thereof.

Exemplary Embodiment 1 (Production of a Cellulose Powder Provided With 18.3 wt % of Elemental Silver and 0.2 wt % of Elemental Ruthenium)

132.45 g of aqueous silver nitrate solution (silver content 36.24 wt %; 445 mmol Ag) and 2.60 g of aqueous ruthenium nitrosylnitrate solution (ruthenium content 19.0 wt %; 4.9 mmol Ru) were added to 364.5 g of demineralized water, and the aqueous precursor solution obtained in this way was mixed homogeneously with 211.2 g of cellulose powder (Vitacel® L-600 from J. Rettenmaier and Sohne GmbH & Co KG) to give an orange, free-flowing impregnated particulate material. 100 mL of this material were subjected to rotary powder analysis at 20° C. by means of the Revolution Powder Analyzer from PS Prozesstechnik GmbH, Neuhausstrasse 36, CH-4057 Basel at 0.5 rpm and using a cylinder with an internal depth of 35 mm and an internal diameter of 100 mm; the frame rate was 10 images per second and 300 avalanches were recorded. The avalanche angle determined in this way was 75 degrees and the duration between two avalanches was 3.6 seconds. To the free-flowing impregnated particulate material, at room temperature, 705 mL of an aqueous hydrazine solution having a pH of 14 [3.68 g (115 mmol) of hydrazine and 71.82 g of a 32 wt % sodium hydroxide solution (575 mmol NaOH), remainder: water] were added at a metering rate of 30 mL/min with stirring. Over time, a black homogeneous pulp which became increasingly easy to stir was formed. After completion of the metered addition, stirring was continued for 30 minutes until no more nitrogen release could be observed. Subsequently, the material was strained off, washed with a total of 1000 mL of water and dried in a drying cabinet at 105° C./300 mbar to a residual moisture content of 15 wt %. By means of ICP-OES, a silver content of 18.3 wt % and a ruthenium content of 0.19 wt % of the end product (based on 0 wt % of residual moisture) were determined.

Exemplary Embodiment 2 (Production of a Cellulose Powder Provided With 10.9 wt % of Elemental Silver and 0.2 wt % of Elemental Ruthenium)

97.96 g of aqueous silver nitrate solution (silver content 36.24 wt %; 329 mmol Ag) and 3.68 g of aqueous ruthenium nitrosylnitrate solution (ruthenium content 19.0 wt %; 6.9 mmol Ru) were added to 554.9 g of demineralized water, and the aqueous precursor solution obtained in this way was mixed homogeneously with 299.2 g of cellulose powder (Vitacel® L-600 from J. Rettenmaier and Sohne GmbH & Co KG) to give an orange, free-flowing impregnated particulate material. 100 mL of this material were subjected to rotary powder analysis at 20° C. by means of the Revolution Powder Analyzer from PS Prozesstechnik GmbH, Neuhausstrasse 36, CH-4057 Basel at 0.5 rpm and using a cylinder with an internal depth of 35 mm and an internal diameter of 100 mm; the frame rate was 10 images per second and 300 avalanches were recorded. The avalanche angle determined in this way was 68 degrees and the duration between two avalanches was 3.0 seconds. To the free-flowing impregnated particulate material, at room temperature, 999.9 mL of an aqueous hydrazine solution having a pH of 13.8 [2.80 g (88 mmol) of hydrazine and 54.66 g of a 32 wt % sodium hydroxide solution (437 mmol NaOH), remainder: water] were added at a metering rate of 30 mL/min with stirring. Over time, a black homogeneous pulp which became increasingly easy to stir was formed. After completion of the metered addition, stirring was continued for 30 minutes until no more nitrogen release could be observed. Subsequently, the material was strained off, washed with a total of 1000 mL of water and dried in a drying cabinet at 105° C./300 mbar to a residual moisture content of 15 wt %. By means of ICP-OES, a silver content of 10.88 wt % and a ruthenium content of 0.21 wt % of the end product (based on 0 wt % of residual moisture) were determined.

Exemplary Embodiment 3 (Production of a Cellulose Powder Provided With 18.9 wt % of Elemental Silver and 1.0 wt % of Elemental Ruthenium)

75.6 g (445 mmol) of solid silver nitrate and 13.94 g of ruthenium nitrosylnitrate solution (ruthenium content 19.0 wt %; 26.2 mmol Ru) were dissolved in 416.8 g of demineralized water, and the aqueous precursor solution obtained in this way was mixed homogeneously with 211.2 g of cellulose powder (Vitacel® L-600 from J. Rettenmaier and Sohne GmbH & Co KG) to give an orange, free-flowing impregnated particulate material. 100 mL of this material were subjected to rotary powder analysis at 20° C. by means of the Revolution Powder Analyzer from PS Prozesstechnik GmbH, Neuhausstrasse 36, CH-4057 Basel at 0.5 rpm and using a cylinder with an internal depth of 35 mm and an internal diameter of 100 mm; the frame rate was 10 images per second and 300 avalanches were recorded. The avalanche angle determined in this way was 73 degrees and the duration between two avalanches was 3.5 seconds. To the free-flowing impregnated particulate material, at room temperature, 705 mL of an aqueous hydrazine solution having a pH of 13.9 [4.19 g (131 mmol) of hydrazine and 81.81 g of a 32 wt % sodium hydroxide solution (654.51 mmol NaOH), remainder: water] were added at a metering rate of 30 mL/min with stirring. Over time, a black homogeneous pulp which became increasingly easy to stir was formed. After completion of the metered addition, stirring was continued for minutes until no more nitrogen release could be observed. Subsequently, the material was strained off, washed with a total of 1000 mL of water and dried in a drying cabinet at 105° C./300 mbar to a residual moisture content of 15 wt %. By means of ICP-OES, a silver content of 18.9 wt % and a ruthenium content of 1.0 wt % of the end product (based on 0 wt % of residual moisture) were determined. 

1. A method for producing a particulate carrier material provided with elemental silver and elemental ruthenium, comprising the following successive steps: a) providing a water-insoluble particulate carrier material and (i) an aqueous solution A comprising dissolved silver precursors and an aqueous solution B comprising dissolved ruthenium precursors or (ii) an aqueous solution C comprising both dissolved silver precursors and dissolved ruthenium precursors, b) bringing the water-insoluble particulate carrier material into contact (i) with aqueous solution A and aqueous solution B or preferably (ii) with aqueous solution C to form an intermediate, preferably an intermediate in the form of a free-flowing impregnated particulate material, c) bringing the intermediate into contact with an aqueous solution comprising a pH in the range of >7 to 14 and comprising hydrazine, to form a mass comprising elemental silver and elemental ruthenium, d) optionally washing the mass obtained after completion of step c), and e) removing water and other possible volatile components from the mass obtained after completion of step c) or d).
 2. The method according to claim 1, wherein the intermediate is a free-flowing impregnated particulate material.
 3. The method according to claim 2, wherein the free-flowing impregnated particulate material has the form of grains or flakes impregnated (i) with aqueous solution A and aqueous solution B or preferably (ii) with aqueous solution C.
 4. The method according to claim 2, wherein the free-flowing impregnated particulate material has an avalanche angle in the range of 40 to 80 degrees, determined by means of rotary powder analysis with 100 mL of the free-flowing impregnated particulate material using the Revolution Powder Analyzer from PS Prozesstechnik GmbH at 0.5 rpm and using a cylinder with an internal depth of 35 mm and an internal diameter of 100 mm at 20° C.
 5. The method according to claim 4, wherein the free-flowing impregnated particulate material is further characterized by a period between two avalanches in the range from 2 to 5 seconds.
 6. The method according to claim 1, wherein the water-insoluble particulate carrier material is swellable with water or is capable of forming a hydrogel.
 7. The method according to claim 1, wherein the material of the water-insoluble particulate carrier material is selected from the group consisting of glass, nitrides, high-melting oxides, silicates, plastics, modified or unmodified polymers of natural origin, carbon substrates and wood.
 8. The method according to claim 1, wherein the water-insoluble particulate carrier material is cellulose powder.
 9. The method according to claim 1, wherein the silver precursors and ruthenium precursors are one or more silver(I) compounds and one or more ruthenium compounds selected from the group consisting of ruthenium(II) compounds, ruthenium(III) compounds and ruthenium(IV) compounds.
 10. The method according to claim 1, wherein the silver:ruthenium weight ratio in the combination of aqueous solutions A and B used in step b) or in aqueous solution C is in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium.
 11. The method according to claim 1, wherein the silver plus ruthenium weight fraction in the aqueous solution C is in the range from 0.5-20 wt %.
 12. The method according to claim 1, wherein the hydrazine concentration of the aqueous hydrazine solution is in the range from 0.1 to 5 wt %.
 13. The method according to claim 1, wherein the aqueous hydrazine solution is brought into contact with the intermediate in a stoichiometrically required amount, or more, for complete reduction of the silver and ruthenium precursors contained in the intermediate.
 14. A particulate carrier material provided with elemental silver and elemental ruthenium and produced according to a method of claim
 1. 15. The particulate carrier material provided with elemental silver and elemental ruthenium according to claim 14, with a silver plus ruthenium weight fraction in the range from 0.1 to 50 wt % at a silver:ruthenium weight ratio in the range from 1 to 2000 parts by weight of silver:1 part by weight of ruthenium.
 16. A use of a particulate carrier material provided with elemental silver and elemental ruthenium according to claim 14 as an additive for antimicrobial finishing of: metal surfaces; coating agents; plasters, molding compounds; plastics in the form of plastics films, plastics parts or plastics fibers; synthetic resin products; ion exchange resins; silicone products; cellulose-based products; foams; textiles; cosmetics and hygiene articles.
 17. The use according to claim 16, wherein the cellulose-based products are selected from the group consisting of paper products, cardboards, wood fiber products and cellulose acetate.
 18. The use according to claim 16, wherein the plastics are selected from the group consisting of ABS plastic, PVC, polylactic acid, PU, poly(meth)acrylate, PC, polysiloxane, phenol formaldehyde resin, melamine formaldehyde resin, polyester, polyamide, polyether, polyolefin, polystyrene, hybrid polymers thereof, and mixtures thereof. 